2011 Prius Front Turn Signal

Sounds like the turn signal relay needs to be troubleshooted next.

 

Just start tracing the circuits back. The wire harness along the bumper (to which the turn signals connect) joins the engine compartment harness at a junction connector behind the driver's corner of the front bumper (ahead of the wheel well liner). From there it's a straight shot back into the cabin and to the instrument panel junction block. There's information here about getting ahold of the wiring diagram.

 

That information is also in the electrical wiring diagram (more info). If you select the connector and click the orange "info" icon down in the lower right of the window (which doesn't say "info" but it is orange and you just have to know what it's for), you'll get the page with the diagram and pinout of the connector, including how the terminal retention mechanisms work (there are usually two). If you click the "(+) wiring harness repair" link on that same page, you will also be shown the part numbers of the repair terminals you need, and the crimp sleeves to be used with them.

Is it only the bumper harness that's damaged, and the mating connector on the car is ok?

If that's the case, I think I'd go ahead and just replace the harness. $75 is not a bad price, you'll save the price of the repair terminals and crimpy bits, plus all your time fussing with it. If you get the harness from a salvage yard you can probably get it around half that; if you get the harness from a model that had the foglights or the radar, it will have the wiring for those too, in case you get upgrade fever later on.

Edit: looks like I saved those diagrams from an earlier project. PDF attached.

It shows the connector as a "double lock type" (as usual), with a "housing lance". That means the primary terminal lock is a little lance that is part of the plastic housing, and drops into a little hole in the terminal. (If it said "terminal lance", that would mean a little bent-out part of the metal terminal, that would click behind part of the housing.)

The second lock mechanism is usually some larger plastic part of the housing, that secures all of the individual lances for the terminals when it is in the locked position. For this housing, I would guess it is the inside part of the housing that is white instead of black, and probably releases when you shift it slightly outward (out the open end of the housing). I apparently didn't save that part.